Protect High Value Tests

Independent Thermal Fail-Safe (IFS)

TotalTemp’s Independent Thermal Fail-Safe Systems provide a truly independent layer of protection for any thermal test environment. Operating outside the primary temperature controller, the IFS is designed to shut down heating, cooling, or DUT (Device Under Test) power when preset temperature limits are exceeded.

This creates a reliable, redundant safeguard against thermal runaway, unintended cooling, loss of cooling capacity, or DUT active-load overheating. IFS units can be retrofitted to most Thermal Platforms, Temperature Chambers, Hybrid Chambers, or custom thermal
systems. Each system is configurable for high-limit or low-limit protection and supports thermocouple or RTD sensing. Audible alarms, visual indicators, and optional digital notifications (via Synergy Nano) provide clear
operator awareness during both attended and unattended testing.

Rackmount and benchtop configurations are available, covering temperature ranges from –200 °C to +1260 °C  suitable for ESS, space simulation, cryogenic testing, and high-temperature materials evaluation.

Redundant Fail-Safe

Figure 2: TotalTemp Technologies’ Controller Interface

The red circle in Figure 2 indicates the redundant high/low-limit temperature controller. A redundant fail-safe with a limit controller works differently than the IFS. It uses an independent RTD sensor to monitor temperature and actuates a redundant cryogenic cutoff valve to physically stop LN₂ flow during cold-runaway scenarios caused by primary valve failure.

In addition to closing the valve, the redundant controller also cuts power to the main relay, removing power from heaters and blowers while keeping the controller energized. Together, the valve and relay shutdown ensure the
chamber or platform cannot continue cooling or heating during an equipment failure, protecting the device under test.

Summary:
IFS = external, controller-independent electrical shutdown
Redundant Fail-Safe = internal, cryogenic-specific mechanical + electrical shutdown. Using both creates a layered, highly robust safety architecture.

How the Independent Fail-Safe Protects the DUT

Figure 3: Temperature Chamber example, Model C460-N

1. An independent sensor monitors DUT or chamber temperature and detects when the safe limit is exceeded.
2. The Fail-Safe removes power from heaters, cooling, or the DUT itself, stopping further heat generation or
   runaway conditions. For cryogenic systems, full protection requires a redundant cryogenic valve, since removing
   power alone cannot stop cooling if a primary valve fails to close. The redundant valve shuts down coolant flow
   and latches in a safe state until manually reset.
3. Audible and visual alarms alert operators. With Advanced Synergy Nano integration, digital notifications can be sent to remote users during unattended cycling.

Application Examples

1. Protecting High-Value Electronics During Thermal Runaway (ESS)

Figure 4: TotalTemp Dual Thermal Platform, Model SD49/98

Scenario: An ESS thermal platform is ramping quickly when a heater relay sticks (SSR TRIAC latches closed).

Fail-Safe Response:

1. Independent temperature sensor detects the over-temperature condition.
2. Fail-Safe cuts power to both the chamber heaters and the DUT, stopping internal heat generation.
3. System alarms and forces a safe shutdown state.

Benefit: Prevents overheating damage, ignition events, or destruction of expensive flight or mission-critical electronics.

2. Preventing Cryogenic Over-Cooling in Space Simulation or Portable TVAC Systems

Scenario: A cryogenic cooling valve sticks open or the primary controller fails low, driving the system far below the intended setpoint.

Fail-Safe Response:

1. Low-temperature limit triggers when the platform or chamber drops below the allowable minimum.
2. Fail-Safe closes the cryogenic valve or shuts down coolant flow.
3. Optional digital notifications alert remote operators during unattended testing.

Benefit: Protects optics, composites, adhesives, and aerospace hardware from cracking or embrittlement due to unintended deep-cold excursions.

3. Stopping a Device Under Test When Heat Cannot Be Removed

Scenario: A DUT generates significant internal heat. If the cooling subsystem fails — blocked coolant flow, compressor fault, pump failure, or depleted LN₂/CO₂ supply — the platform can no longer remove heat. Even with heaters off, the DUT temperature rises due to its own internal power dissipation.

Independent Fail-Safe Response:

1. Independent sensor detects rising DUT or platform temperature.
2. Removes power to the DUT, stopping internal heat generation.
3. System alarms and prevents restart until cooling capability is restored.

Benefit: Prevents DUT burnout, battery thermal events, or runaway heating in RF, laser, or avionics modules — including during long or unattended tests.

Thermal Testing Limit Safety Overview

Temperature chambers and thermal platforms inherently carry risks when operating at extreme temperatures.
Protecting both the test article and the equipment requires multiple layers of safety:

1. Temperature Controller limits: Prevent users from requesting unsafe temperatures.
2. User-set limits: Protect sensitive DUTs from accidental over-temperature conditions.
3. Alarm shutdown modes: Triggered when the primary sensor reads outside the allowed range, controller outputs turn off and alarm is logged by Synergy.
4. Independent Fail-Safe and Limit Controller: Provide protection when control functions fail, equipment malfunctions, or human error occurs.
5. Redundant Fail-Safe with cryogenic valve: Essential for cryogenic systems where removing power alone cannot stop cooling.
6. Active load shutdown: Ensures high value device under test (DUT) or high-velocity blowers cannot continue generating heat after a fault.

In Summary

TotalTemp’s Independent Thermal Fail-Safe Systems provide a fully independent layer of protection for thermal test
environments and ESS applications. Operating separately from the primary temperature controller, they automatically shut down heating, cooling, or DUT power when preset temperature thresholds are exceeded.

This architecture delivers a redundant safeguard against thermal runaway, unintended cooling, loss of cooling capacity, and active-load overheating. Each unit supports high- or low-limit protection using thermocouple or RTD
inputs. Audible alarms, visual indicators, and optional digital notifications via the Advanced Synergy Nano controller ensure clear operator awareness during both attended and unattended testing.

Next in Part II

In our next blog, we will cover essential maintenance and monitoring practices to ensure smooth, trouble-free, and time-efficient thermal testing. For more information about our Independent Fail-Safe and Redundant Fail-Safe
systems, please contact us — we are always happy to support.